Power transmission mechanism



Dec. 2,1947. E. s. SEGARD 2,432,077

POWER TRANSMISSION MECHANISM '7 Sheets-Sheet 1 Filed Sept. 20, 1940 Dec, 2, 1947. E. s. SEGARD POWER TRANSMISSION MECHANISM Filed Sept. '20, 1940 '7 Sheets-Sheet 2 Dec. 2, 1947. E. s. SEGARD POWER TRANSMISSION MECHANISM Filed Sept. 20, 1940 7 Sheets-Sheet 3 Dec. 2, 1947. E. s. SEGARD POWER TRANSMISSION MECHANISM Filed Sept. 20, 1940 7 Sheets-Sheet 4 H fwgg Dec. 2, 1947. E. s. SEGARD' POWER TRANSMISSION MECHANISM Filed Sept. 20. 1940 7 Sheets-Sheet 5 Dec. 2, 1947. I E s, sEGARD 2,432,077

. POWER TRANSMISSION MECHANISM Filed Sept. 20, 1940 7 Sheets-Sheet 6 Dec. 2, 1947. s, sEGARD 2,432,077 POWER TRANSMISSION MECHANISM I Filed Sept. 20, 1940 I 7 Sheets-Sheet 7 ,l rg. 14.

Patented Dec. 2, 1947 NITED STATES ATENT OFFICE Section 10, Public Law 690, August s, 1945 Patent expires September 20, 1960 This invention relates to improvements in power transmission mechanisms.

It is a device for the transmission of power from a power source such as an engine or a motor, to the Vehicle, conveyance or machine to be propelled by the power source. It is a power transmission in which the power from the power source to the vehicle, conveyance or machine propelled, is delivered through a series of speed changes through the automatic interposition of constantly meshed gear trains of varying reduction ratios, which interposition of the various gear trains is automatically effected through the coaction oi the velocity of rotation, and the torque resistance of the vehicle, conveyance or machine propelled, and the torque delivered by the power source, the action of the velocity of propulsion, the torque resistance of the vehicle, conveyance or machine propelled, and the torque delivered by the power source being inter-opposed and inter-controlled in such manner that the velocity responsive means never escapes the opposition or the control of the torque responsive means and the torque responsive means never escapes the opposition and control of the velocity responsive means.

A principal object of the invention is to produce power transmissions with constantly meshed gears and constant flow of power automatically through a series of speed changes or gear ratios in such manner as to enable the power source to constantly operate within its economical range of velocity and torque capacity.

Another object is to provide such a power transmission mechanism, wherein the change of gear ratio between the prime mover andthe driven device may be accomplished quickly and with a minimum of effort.

Other objects and advantages reside in details of design and construction which will be more fully disclosed in the following description and in the drawings wherein like parts have been similarly designated and in which:

Figure 1 is a longitudinal sectional view of transmission mechanism that embodies the present inventive concept;

Figure 2 is a plan view, partially in section, of the mechanism illustrated in Figure 1;

Figure 3 is a cross sectional view taken along the line 3-3 of Figure 1;

Figure 4 is a cross sectional view taken along the line '54 of Figure 1;

Figure 5 is a cr ss sectional view taken along the line 5-5 of Figure 1;

5 Claims. (Cl. 74-336) .ferred embodiment of my c utch housing member 29 to member 33 Figure 6 is a cross sectional view taken alon the line 6-5 of Figure 1; v

Figure '7 is a partial sectional view taken along the line 'l--1 of Figure 1 and illustrating certain components of the device;

Figure 8 is a partial sectional view taken along the line 8-8 of Figure 1, illustrating certain components of the mechanism;

Figure 9 is a fragmentary view illustrating certain details shown in Figure 1, in a top or plan View; 1

Figure 10 is a fragmentary longitudinal section of certain details shown in Figure 1;

Figure 11 is a fragmentary view, partially in section, of certain details shown in Figure 10;

Figure 12 i a sectional view taken along the line l2--I2 of Figure 10;

Figure 13 is an exterior elevation of the mechanism illustrated in Figures 1 and 2 and showing the same enclosed in a suitable housing: and

Figure 14 is an exterior plan view of the mechanism illustrated in Figure 2, as it would appear enclosed in a suitable housing, a portion of which housing is broken away to show certain control features.

In order to disclose an operative reduction to practice of the present invention, the accompanying drawings, which are made a part hereof, will be described in some particularity. However, this disclosure is intended to present a typical example and should not be construed to express or to imply any limitation to this invention, the scope of which is, in reality, measured by the appended claims.

In the drawings, Figure 1 illustrates a preinvention. The numeral 2B denotes the rear end of the driving shaft of a prime mover, such as an automobile en ine or the like. Flange 2| integral therewith. is bolted to hub 22 by bolts 23. On the rear surface of disk 2 of hub 22, integrally attached, is friction disk 25. Di k 24 through bolts 26 is attached to the clutch housing comprised of housing members 21. 28 and 29. Housing member 28 and 29 are joined by bolts 30. In housing member 29 are n ne equidistant spring-containing recesses 3| and spring gu des 32 carrying springs 33. Housing member 29 is mounted on bearing 34, which bearing is held in its recess by retainer 35.

Linkage members 36, 31 and 38 connect the of the clutch release collar mechanism comprising members 39, 4!] and 4| and thrust bearing 42. Clutch'rele se mechanism member 4! is connected to a selectively operable clutch release mechanism not shown in Figure 1 but illustrated elsewhere.

Clutch release collar member 49 is slidably mounted on splined tubular shaft 46 of pressure plate disk 41, and pressure plate disk 41 is slidably mounted on splines 48 of which there are several on the inner circumference of clutch housing member '29. Pressure plate disk 41, through bolt 49, is connected to pressure plate 50. Pressure plate 50 is splined in housing member 28 on splines I.

Clutch plates 52, of which there arethree, are also mounted in housing member 28 on splines 5|. Clutch plates 52 and pressure plate 59 are retained in housing member 28 by retaining flanges 53 and 54. Clutch plates 55, of which there are four, are mounted on splines 48. of housing 29, and pressure disk 56 of clutch housing member 29 is integral therewith. "Clutch plates 51, of which there are five, are mounted on splines 58 of hub 59 and are held thereonlby retaining nut 60. Hub 59 fis'in'ounted on bearing 6| and is connected totubular shaft 62 in driving relation therewith, through a, splined connection 63.

Gear and gear 65 are integral with'tubular shaft 32. The rear end of shaft 62 is mounted on thrust bearing 66 and just forward of gear in bearing '61. "Gear 64 meshes with gear '68 and gear 65 meshes with gear 69. Gear 68 is rotatably mounted in bearings 19 and H and is connected in driving relation with slidable shaft 12 through splines 13 onthe enlarged forward end of slidable shaft 12; Slidable shaft 12 at its rear end is slidably mounted in bearing 14 and its forward end slidably mounted in the splined hub of gear 68. Gear 69 is mounted on bearing 1i and in bear-ing 1-5, which bearing is mounted in recess I68. Gear 459 is connected with collar 11 through spli-ned connection 18, which collar 11 containing bushing 19 is rotatably but not slidably mounted on slidablesha'ft 12. Notched wheel '89 is integral with collar 11. Gear 81 ismoun't'ed on bearing 82, which bearing is mounted on collarl l. Hub 83 of gear 8| contains centrifugally operative dog 34, which dog carri'esbolt 85 and springs 86, of which there are two each, and is provided with teeth 43-! and 88 best show-ni'n Figure 8.

Gear '8I, when at rest and when rotating below "a predetermined speed, is connected in driving relation with notched wheel 99, Figure 7,'trirough tooth-81 of 'dog '84. 'Wh'ee18'9, which is an internally no'tched wheel, is'mounte'd integrally on slidable shaft 12 and, therefore, is in driving relation with gear 68 "through 'splined connection 13 of slidable shaft 12. Internally notched wheel 89, when rotating above a predetermined speed, is connected in driving relation with gear-81 through V tOO'th 88 of dog '84.

Gear 8| meshes with gear 99, which gear 99 comprises two elemehtsgear'BDand rim-section 9| which is riveted to gear '99. 'Gear 99 and rim section 91 are mounted on bearings '92 and 93. Rim section 9'I, 'below predetermined speeds, is

connected in driving relation unidirectionally with 4 plates I02 in driving relation through splines I93 and are held ther by retaining nut I04. Tubular shaft I 0|, which is the forward end of tubular shaft 98, carries splines I95 on its inner surface. Hub I96, splined on its outer surface as indicated at I01, is slidably mounted in splines I05 of tubular shaftIM. I-Iub I96 is integral with disk I08. On the outer surface of tubular shaft IOI is mounted slidably hub I 09, and bolts I I9, of which there are three, are integral with hub I99. On .bolts II9 are slidably mounted wedge-shaped weights III, and on bolts II9, acting against weigh-ts H I, are'springs II2 retained by nuts li3. Weights I II are in slidable contact with disks I09 and 198 through tongues I I4 integral with weights :III and lips H5 integral with disks I 99 and I08.

In weights "III are mounted two pairs of rollers H6 and II! on bolts H8 and H9, respectively, which pair of rollers contact each other at point I29 and contact disks I99 and I68 on race HI and rac 1-22, respectively, which are converging inner surfaces of said .disks I 99 "and I98. Hub I96 on its inner surf-ace carries female screw threads 123, which engage corresponding male screw threads 1240p the forward 'endof'shaft I25. The forward end of driven shaft I25 is journalled in thrust bearing I26 mounted in hub 22 of disk 24.

The rear end of shaft is journalled in thrust bearing 121, just forward of which is thrust collar 128 integral with said shaft I25. Flange I29, integral with thrust 'collar I28 and driven shaft 425, carries splines I39 on its outer surface and recesses I31, of which there are three. Inside flange 129 rides rotatably the hub of hub section 94. slidably mounted on splines I 39 is ratchet clutch-carrying housing I32 with ratchet teeth 133, which teeth I33, when moved forward, grasp ratchet teeth I34 on rear surface of gear 99.

Mounted in ratchet clutch-carrying housing I32 are plungers I35, actuated by springs I37 in :recess I36, of which there are three. I-n housing 432 there is alsomounted in recess I38, spring I39 on guide I49. On the rear hub end of ratchet clutch-carrying housing I32 is groove MI, in which groove is mounted shifting collar I42, which collar carries pivots I43. Pivots I43 are mounted in slots I44 of shifting lever arm I45. On the rear hub end .of internally notched wheel 89 is groove I 46, in which groove is mounted shifting collar 141 which carries pivots I48. Pivots I48 are mounted in slots I49 ofshifting lever I59.

Bearing 15! journals a shaft I52, on which shaft is mounted rotatably andslidably hub I53 integral with the reversing gear, which reversing gear cannot be seen in Figure 1. At the rear end of hub I53 is groove I54, in which groove is mounted shifting collar I55 which carries pivots I56. Pivots I56 are mounted in slots I 51 of shifting lever I58.

The assembly above enumerated is mounted in 'a support and enclosing casing comprising members I59, "I69 and I6I joined by bolts I52 and I63, which casing is attached to the motor block by tap screws I64. Bearing MI is mounted in recess I65 in casing member I69. The forward end of shaft 152 is mounted in bearing I '86 in recess I61 of casing member I59 (bearing I66 and recess I61 cannot be seen inFigure 1 because they are below structures appearing in the drawing).

Figure 2 illustrates a top plan of the mechanism shown in Figure 1 and hereinbefore described, with the top half of the enclosing and supporting casing in section, and a fragmentary view of the velocity responsive torque controlled means.

Figure 3 shows a section taken on the line 3-3 of Figure 1, looking in the direction of the arrows and disclosing the velocity responsive means.

Figure 4 is a section taken on the line 4-4 of Figure 1, looking in the direction of the arrows, showing casing I59 in elevation forward of line 4-4 in Figure 1, and in section on line 4-4 of Figure 1, showing clutch casing member 29 and pressure plate disk 41, release levers 38, linkage 31 and 35 in elevation, members 39 and 40 of clutch release collar mechanism, shaft 46, shaft 62, shaft 93 and driven shaft I25 in section.

Figure 5 is a section on line 5-5 of Figure 1 looking in the direction of the arrows, showing casing member I59 in elevation and casing member I60 in elevation forward of line 5-5, and in section on line 5-5 of Figure 1, and gear 69 in elevation, collar Ti and shaft I2 in section and the unidirectional clutch rim section member ill in section, and balls 95 in elevation and hub section 94 of the unidirectional clutch mechanism in section, together with shaft 98 and driven shaft I25 in section, gear I14 (the forward half) of the reversing gear in elevation, reversing gear hub I53 in section, bushing H6 in section and shaft I52 in section.

Figure 6 illustrates casing member I59 in elevation and easing member I65 in elevation forward of line 5-5 of Figure 1 and in section on line 8-6 of Figure 1, together with gear 90, gear 69, the reversing gear comprising gears I14 and I15 (which are cast integral with hub I-53, which hub cannot be seen in this figure) and bearing I5l in elevation, and the shiftable means mounted on thrust shoulder I28, shaft 72 and hub I53, respectively (hub I53 cannot be seen in Figure 6).

The shiftable means mounted on thrust shoulder I28 being shown partly in elevation and partly in section and comprising collar I42, pivots I43 thereof and lever I45, which lever I45 is pivoted on bolt I13 in casing member I60 and carries pull rod IT! which is pivoted in lever I45 by bolt I19.

The shiftable means mounted on shaft 12 is shown in elevation and comprises shifting collar member l4! and pivots I48 thereof and lever I50, which lever is pivoted in casing member I60 on bolt 180. Lever I58 carries pull rod I8I which is pivoted in lever I50 by bolt I82.

The shiftable means mounted on hub I53 is fragmentarily shown in elevation and comprises collar 155, pivots I55 thereof and lever I50, which lever I58 is pivoted in a fulcrum member N3 integral with casing member I60 and is shown in section. Lever 158 on its upper end carries pull rod I84 which is pivoted on bolt I85 in lever I58.

Figure 7 shows in section, the following members: internally notched wheel 89, dog 84, tooth 88 of dog 84, tooth 81 of dog 84, hub 83 of gear BI, externally notched wheel 88, bushing 19 and shaft I2.

Figure 8 shows the external portion of internally notched gear 89 in elevation and the rear flanged portion of internally notched gear 89 in section and dog 84 in section, tooth 88 and tooth 81 of dog 84 in elevation, bolts 85 in elevation and springs 86 in section and elevation and hub 83 of gear 8| in section and showing externally notched gear 58 in elevation, together with bushing I9 in elevation and in elevation the recesses I85, I81 and 583 in the hub 83 of gear 8| (in which recesses operate dog 84, bolts 85 and springs 85) and shaft I2 in section.

Figure 9 is a fragmentary detail combination elevation and section drawing, the section portions of which show a section through Figure 8 on line 9-9 looking in the direction of the arrows. The drawing comprises the following countershaft assembly members shown in Figure 1 and Figure 8: gear 8|, hub portion 83 of gear 8|, dog 84, tooth 88, bolts 85, internally notched wheel 89, hub I13, the rear end of internally notched wheel 83 carrying groove I45, and shaft I2.

Figure 10 illustrates the velocity responsive torque controlled mechanisms, showing shaft I25, thrust collar I28, flange I29 with recess I3I, rim section 9I of the unidirectional clutch mechanism, hub section 94 of the unidirectional clutch mechanism, tubular shaft 08 with male screw threads 91, tubular shaft 20! with spline I05, hub I06 with female screw threads I23, pressure disks I00 and I08 carrying lips H5 and races I2I and I22 and weight III, showing tongue II4, rollers H8 and in, tap screw shafts H8 and H9.

Figure 11 discloses the integral structure of driven shaft 625, thrust collar I28, flange I29 and splines I30 and recess I3I.

Figure 12 illustrates driven shaft I25, thrust collar I28, rear face of flange I29 and splines I30.

Figure 13 shows the enclosing casing and the clutch pedal assembly comprising pedal 45, link I98, lever I89, key I94, clutch release shaft 44, pivot 'I 9 I retaining nut I92, clutch assembly window cover I93 retained by tap screws I95.

Figure 14 illustrates the enclosing casing and the clutch pedal assembly, together with a view through a cutaway portion of the enclosing casing through which can be seen clutch release lever 43 and clutch release shaft 44 integral with clutch release lever 43.

Operation of the device when torque is supplied progressively increasing the rate of rotation Assuming that the device shown in Figure 1 is installed in a vehicle or machine in such manner that shaft 20 is the rear end of the crankshaft of the motor or of the driving shaft of whatever power source is being utilized and that the direction of rotation of the power source be counter-clockwise directional when viewed from the rear, then the device will operate in the following manner: shaft 20 being set in rotation, rotates in unison with it by reason of integral construction the following elements, flange 2|, disk 24, the clutch housing comprising housing members 21, 29 and 29, friction disk 25, clutch plates 52, pressure plate 50, pressure disk 58 with its hub and bearing retainer 35, clut"h plates 55, pressure plate disk 47, the clutch release collar mechanism comprising members 39, 40, levers 38, linkage 31 and 38, all of which structures revolve on bearing 34, which serves to keep the aforementioned clutch housing in alinement with shaft 20.

With the foregoing structures attaining a sufficient speed of rotation to enable the power source to deliver sufficient torque to pull the vehicle, pressure on clutch pedal 45, Figure 13, which has been holding clutch pressure plate 4'! in the position of release through clutch pedal shaft 44, clutch release lever 43 and clutch release collar mechanism members M, 42, 48 and 39, is gradually released. This release of pressure on clutch pedal 45 permits springs 33, acting on pressure plate 58, to move pressure plate 41 through the intermediary of bolts 49, which movement of pressure plate 4'3, it being splined in housing member 29 on splines 48, together with clutch causes hub section 94, at once,

plates .55, puts .into operation the friction plate clutch mechanism comprising pressure plate 41, clutch plates'! and clutch plates 55 and pressure plate .56.

Clutch plates 51 being mounted on splines 58 of hub 59 and retained thereon by retaining nut 6.9, are in driving relation with tubular shaft 62 through splines 63, and therefore cause tubular shaft 62 to rotate in unison with shaft .29 and the clutch housing at the moment the aforementioned clutch thus becomes engaged.

Tubular shaft 62 being integral with gears .64 and 65, causes gears 64 and 65 to likewise rotate in unison with the clutch housing and shaft 29. Gear 54 rotates gear 69 and gear 65 rotates gear 99. Gear 69 being in driving relation with shaft 72 through spline connection 73 on the enlarged forward portion of shaft I2, rotates shaft I2 at a speed commensurate with the circumferential measurement of gear64 and gear 68.

.Gear 65 meshing with gear69, rotates gear 69 at a speedcommensurate with the circumferential measurements of gear .65 and gear 69, and internally splined hub 76 of gear .69, being in driving relation with collar I1 through spline .78, rotates collar "IT in unison with said gear 69. Collar 'I'I', being rotatably mounted on shaft I2, on bushing I9, is integral with notched wheel 99.

Notched wheel 99, below a predetermined speed, is connected in driving relation with gear 8| through tooth 8?, Figure '7, of dog 84, by virtue of dog 84 being urged toward the center of its rotation by springs 96 through bolt 85 because the mechanism, dog 94, bolt .85 and spring 86, is slidably mounted in the hub of gear 8|. Since gear 8| is in driving relation with gear 99, as just described, and meshes with gear 99, it rotates gear 99 at a speed commensurate with the circumferential measurements of gear BI and gear 99.

Gear 99 being constructed integrally with rim section 9|, begins to rotate rim section 9| in counter-clockwise direction at the moment of the engagement of the fri tion clutch above described. When the rim section 9| begins to rotate in counter-clockwise direction, balls 95 which are acted upon by plunger-s I69 through the urge of springs I I9, Figure 5, become impinged between rim section 9| and hub section 94 in the race as shown in Figure 5. This impingement of balls 95 in the race as shown in Figure 5, to rotate in unison with rim section 9|, resulting in integral driving relation unidire tionally between gear 99 and female screw threads 96 on the inside of hub section 94. Female screw threads 96 inside hub section 94 meshing with male screw threads 91 on the outer surface of the rear end of shaft '98, cause shaft 98 to be driven in counter-clockwise direction and to be urged forward, i. e., to the right as viewed in Figure 1, with a force proportional to the pitch of screw threads96 and '91.

Tubular shaft 98 is rotated in counter-clockwise dire tion and is inte ral with tubular shaft I 9| and carries splines I 93. on which splines are mounted clutch plates I92. Just forward of clutch plates I92 is pressure disk I99. also integral with shaft 98. Tubular shaft I9I, inte ral with 98, as stated, is splined on its inner surface at I95.

In splines I95 rides hub I96. which hub I96 at its forward end is integral with pressure disk I98. Hub I,96, in drivingrelationwith tubular-shaft -I9'I, through splines I95, is rotated in counter-clockwise direction in unison with tubular shaft 98.

Hub I96 on its inner surface carries female screw threads I 23, which engage male screw threads I24 of driven shaft I25, and therefore hub I96 rotates driven shaft I25 in counterclockwise direction and is itself urged towards the rear,.i. e., to the left as viewed in Figure 1, by a force proportional to the pitch of said screw threads I23 and I24, by reason of the fact that driven shaft I25 is prevented from moving forward by the hub of hub section 94 operating against flange .I29 .and thrust collar I28 with an equal :force.

As a consequence of the driving relationships above described, it follows and will be readily seen that driven shaft I 25 is now rotating at a speed below the speed of rotation of driving shaft 29 in accordance with the gear ratios obtaining in the gear train comprising gear 65, gear 69, gear 8| and gear 99, and that tubular shaft 98 is being urged forward, i. e., to the right as viewed in Figure 1, and hub I96 is being urged rearward, i. e., to the left, by forces proportional to the pitch of screw threads 96 and 91 and the pitch of screw threads I24 and I23, respectively.

Pressure disks I99 and I98 being integral with tubular shaft 98 and hub I99, respectively, are being urged towards each other by the amount of the same respective forces just described. Pressure disks I99 and I98 on their surfaces, facing each other, are constructed with inclined plane faces, between which are mounted Weights II I carried on bolts II9, which bolts are integral with hub I 99, which hub is slidably mounted on tubular shaft I9I. Springs ||2 urge said weights III toward their common axis of rotation. Weights III being radially slidable between converging inclined surfaces of pressure disks I99 and I99, rotate in unison with tubular shaft '99 and pressure disks I 99 and I98 because of tongue H4 and lip H5, and thereby control the axial positions and relationship of the pressure disks I99 and I98.

Weights III, through the intermediary of rollers H7 and IIS operating against the inclined faces of disks I 99 and I98, urge said pressure disks I99 and I98 away from each other by an amount of force proportional to the mass of the weights and the rate of rotation of driven shaft I25 by virtue of the action of centrifugal force.

Because of the mechanical advantage inherent in the gear train comprising gear '65, gear 69, gear 8| and gear 99, and the pitch and direction of screw threads 9'! and I24, the torque resist ance of driven shaft I25 is greater than the torque supplied by the power source, and it will be readily seen that below a predetermined speed level the force urging pressure disks I99 and I98 towards each other is much greater than the centrifugally inspired force urging pressure disks I99 and I98 away from each other by the action of weights III.

With an increase in the rate of rotation of driven shaft I25,,due to the ability of the power source to accelerate, the ground speed of the vehicle reaching a point where the mechanical advantage of the gear train comprising gear 65, gear 69, gear 8| and gear 99, is no longer necessary, then momentary deceleration of the motor causes release of the pressure in notch I99 of wheel 89 against tooth 81 of dog 84, whch release of pressure permits the centrifugal force acting on ,dog 8.4 to overcome the action of springs 86 with the result that dog 84 moves away from the center of rotation and instantaneously tooth 88 of dog 84 becomes seated in the immediately oposite notch I98 of internally notched wheel 89. Internally notched whee1 99 is mounted integrally on shaft 12 and therefore is in driving relation with gear 68, and consequently causes gear 8| to rotate in unison with gear 68, whereby gear 90 at once rotates in accordance with the ratio of rotation obtaining in the rear train comprising gear 99, gear 68, gear BI and gear 90.

Coincidental with the momentary deceleration of the power source, the force urging pressure disks I and I08 towards each other, becomes interrupted by reason of the momentary cessation of torque transmittal through screw threads 96 and 91 and I23 and I24, respectively, which cessation of torque transmittal permits weights Hi to move away from the center of rotation, pushing pressure disks I90 and I08 away from each other by a force proportional to the centrifugal force acting on weights III and the inclined plane relationship between rollers H6 and H1 and pressure disks I00 and. I08, respectively.

The pushing apart of pressure disks I00 and I98 causes said pressure disk I08 to come in contact with friction surface 25 and causes said pressure disk I99 to effect engagement of clutch plates 52 and I97. between pressure plate 50 and pressure disk I90, which engagement tends momentarily to urge shaft 98 to rotate in unison with the clutch housing and driving shaft 20. Gear 99, through the engagement of tooth 98 of dog 84 inthe immediately opposite notch I98 of internally notched wheel 89, having come to rotate in accordance with the gear ratio of gears 94, 69, 8! and 90, causes resumption of torque transmittal through screw threads 96 and 91 and I23 and I29. Immediately upon the resumption of acceleration of the motor after the momentary deceleration, the resumption of torque transmittal through screw threads 96 and 91 and screw threads I23 and I24 causes the torque inspired force urging pressure disks I00 and I98 towards each other to be resumed, which immediately urges weights |I| towards the center of rotation back to their original position, thereby completely preventing the tendency to engagement between pressure disk I90, clutch plates 52 and I02 and pressure plate 50, and between pressure disk I 09 and friction surface 25.

The torque inspired force urging pressure disks I00 and I08 towards each other and urging weights towards the center of rotation, is now proportional to the torque of the gear train transmitting it, which is, of course, lessened proportionately to the lessened mechanical advantage of the gear train comprising gears '64, 98, 8| and 99. Further acceleration of the motor causing an increase in the centrifugal force operating on weights III, increases the force by which weights III are urging pressure disks I00 and I08 away from each other.

As the acceleration of the vehicle with the consequent lowering of torque resistance of driven shaft I25, by virtue of the lessening of the inertia of the vehicle and/or changes in terrain over which the vehicle is operated, the torque resistance of driven shaft I25 i reduced, which results in consequent further reduction of the force urging pressure disks I00 and I98 towards each other because of the decrease of the torque transmittal through screw threads 96, 91, I23 and I24. This causes the force urging pressure disks I00 10 and 08 towards each other to become insuflicient to oppose the force with which weights I urge pressure disks I00 and I08 away from each other.

With the torque inspired force urging pressure 5 disks I00 and I08 towards each other insuflicient to oppose said centrifugally inspired force with which weights III are urging pressure disks I90 and I08 away from each other, said pressure disks I00 and I08 move apart as the torque resistance 10 drops or the centrifugally inspired force increases with the result that pressure disk I00 moves rearward sufficiently to cause engagement of clutch plates 52 and 102 between pressure plate 50 and pressure disk I00, and pressure disk I08 comes in contact with friction surface 25, which engagement causes shaft 98 to come to rotate in unison with the clutch housing and driving shaft 20.

Immediately upon this engagement of this centrifugally responsive torque controlled clutch and shaft 98 coming to rotate in unison with the clutch housing and driving shaft 20, hub section 94 begins to rotate at a speed greater than rim section 9|, which action immediately releases balls 95 from their position of impingement in the races in the hub section 94 and rim section 9|, thereby effecting release of the driving relationship between rim section 9| and hub section 94.

It will be readily seen that now at the speed at which driven shaft I25 and driving shaft 20 are rotating in unison, the driving relationship between driving shaft 20 and driven shaft I25 is a direct drive relationship and that the gear train comprising gear 90, gear 8|, gear 68 and gear 64 no longer transmits power.

Furthermore, it will be noted that with the engagement of the centrifugal responsive torque controlled mechanism, weights I have moved away from their center of rotation and have come to rest against the inner surface of clutch housing member 21 and springs 33 have been compressed and pressure plate 50 has been pushed backward against retaining flange 53, whereby because of the connection between pressure plates and 41 by virtue of bolts 49, clutch plates and 51 have become disengaged. Therefore, the gear train comprising gear 64, gear 68, gear BI and gear 90 is no longer being urged to rotate 0 except through the friction present between balls 95, rim section 9| and hub section 94 by virtue of pressure of plunger I69 on balls 95 exerted by springs I10.

It will also be noted that since the momentary 55 deceleration of the motor which released tooth 81 of dog 84 from the notch I99 of externally notched wheel 80 and the consequent severance of driving relationship between gear 69 and gear 8|, there has been no transmittal of torque by so gear and gear 68 and notched wheel 80, but

these members have merely idly rotated in accordance with the gear ratio between gear 65 and gear 69.

With the speed of rotation at the level at pres- 65 ent obtaining, no further phenomena transpire. With a further increase in acceleration, when suificient rate of rotation is attained, the centrifugal force operating on the balls 95 will urge balls 95 outward in their race sufficiently to com- 7 press springs I10, thus removing the friction previously obtaining between them and their race in hub section 94, seen in Figure 5.

Therefore, hub section 94 will cease to urge rim section 9| to rotate until rim section 9| decelerates sufficiently for this friction to reappear.

This means that rim section 9| is never urged to rotate above a predetermined level and that level being the rate of rotation sufficient to produce enough centrifugal force acting on the balls 95 to compress springs I10, therefore gear 910, gear 8|, gear .69, gear 65, tubular shaft 62, hub 59 and clutch plates 51 are never urged to rotate at a speed greater than 'thatrequired to produce sufficient centrifugal force to enable balls 95, acting on plungers I63 to compress springs I10 sufficiently to remove friction between balls 95 and the race on the face of hub section 94 while the velocity responsiye torque controlled clutch is engaged.

When the vehicle is operating at a speed surficient to maintain in engagement the velocity responsive torque controlled clutch, or in other words, maintain direct drive or what is conventionally termed high gear driving connection,

terrain or driving conditions are encountered which increase the torque resistance of driven shaft I25 sufficient to begin to decelerate the motor, then this progressive deceleration of the motor due to this increased resistance of driven shaft 125, decreases the centrifugal force acting on weights III, thus permitting screw threads 124 of driven shaft I25 to urge pressure disk I08 rearward and in like manner, pressure disk I forward by screw threads 97 of shaft 98, which movement of 'disks I00 and I 08 toward each other results in weights I'II being urged towards their center of rotation.

Since weights II I are urged towards their common center of rotation, centrifugal force is decreased with the result that the force by which these weights oppose the movement of disks I08 and I00 toward each other is decreased.

Decrease of the centrifugal force acting on weights II-I decreases the force which pressure disk I00 is exerting on the forward face of pressure plate 50, which pressure plate 50 is urged forward by springs 33 acting against the rear face of pressure plate 50. It follows, therefore, that as the centrifugal force acting on weights III is decreased, the force acting against pressure plate 50-compressing springs 33 decreases proportionately. This is because the force exerted by pressure disk I00 against pressure plate 50, and therefore against springs '33, results from the centrifugal force of weights I I I urging-pressure disks I00 and I08 away from each other, it follows, naturally, that decrease in the centrifugal force acting on weights III proportionately decreases the force compressing springs .33.

Therefore, when there has been suflicient progression in the decrease of the centrifugal force acting on weights III, the force of pressure disk I00 against pressure plate '50 is insufficient to maintain compression of springs 33, wherefore pressure plate 50 is moved forward until 'prevented from moving farther by bolts 49 causing engagement of the manually releasable clutch, just forward of member 41,

It should be'noted that the ability of pressure disk I00 to exert force rearward against pressure plate 50 through the intervening clutch plates 52 and I02, is founded :upon the fact that pressure disk I08 is in contact with friction surface 25 of member 24 and therefore is incapable of being moved further :forward. Because of this, all of the motion of pressure disks I00 and I08 away from each other resulting from weights I II moving outward .on the inclined surfaces of the disks I00 and 2108 :during the phase of application of the clutch, was necessarily the property of pressure disk I00 only. Consequently, during the phase of decrease of the centrifugal force acting on weights I II, springs 33 opposing rearward motion of pressure disk I00, become capable of overcoming the centrifugal forces rearward motion of pressure disk I00 and therefore, of course, push pressure disk I00 forward.

At the moment that the springs have pushed pressure disk I 00 forward sufficiently to allow the said springs to cause engagement of the manually releasable clutch represented by member 4'1 and the multiple disk clutch just forward thereof, torque delivered by the driving shaft 20 is at once again transmitted to tubular shaft 62 and therefrom on through the intermediate speed gear train.

This torque transmittal through the gear train causes engagement of the unidirectional clutch.

Engagement of the unidirectional clutch re ults at once in the torque delivered to tubular shaft 98 being increased by the mechanical advantage of the intermediate speed gear train. This 1ncrease in torque transmitted to and through tubular shaft 98, obviously, increases proportionately the force urging pressure disk I 00 forward and pressure disk I08 rearward, i. e., the force urging pressure disks I00 and I08 toward each other.

This increase in the force urging pressure disks I00 and I08 towards 'each other completely overcomes the centrifugal force operating on weights III, wherefore weights III are forced to their position of release resting on hub I09. Obviously, therefore, the resumption cf torque transmittal through the intermediate speed gear train effects prompt release or disengagement of the velocity responsive clutch but does so resiliently because of the integrated relationship with the manually releasable clutch.

The vehicle is now once again operating in intermediate speed or What is commonly termed second gear. When at any time while the vehicle is thus operated, conditions of terrain or other causes of increase in the torque resistance of driven shaft I25, slow down the motor to a point where the operator deems it feasible to use the first gear or slow speed driving connection after the motor has been slowed d wn to the predetermined level at which springs 86 of dog 84 are capable of successfully opposing the centrifugal force operating on dog 84, then the operator obtains the slow speed connection by momentary deceleration of the motor, or momentary application of foot pressure on clutch pedal 45, resulting in release of tooth pressure of notch I98 of internally notched wheel 89 on tooth 88 of dog 84, permitting springs 00 .to pull dog 84 towards its center of rotation, promptly seating tooth 81 in notch I99 of externally notched wheel '80. Re-acceleration of the m0- tor or release of foot pressure on clutch pedal 45, immediately after the momentary deceleration of the motor, causes the vehicle to proceed in low speed or first gear, from which time on, the terrain and driving conditions permitting, the vehicle may be accelerated up to the speed limit of the motor in exactly the same manner as was described for operation of the device when torqu is supplied progressively increasing the rate of rotation.

Having traced the operation from the beginning of rotation of the motor with the vehicle at a standstill up to apredetermined speed, the phenomena occurring while bringing the vehicle 13 to a stop through the medium of applying the brakes of the vehicle will be described.

It will be noted that the pedal controlled clutch has been automatically released since the direct drive relationship has been inaugurated and it is therefore only necessary to hold pedal 35 in the depressed position while bringing the vehicle to a stop by applying its brakes. Immediately upon closing the throttle and thereby causing the compression of the motor to exert decreasing torque, the direction of torque applied through screw threads 95, 9?, I23 and I2tl is reversed, with the result that this diminishing torque urges pressure disks I and I08 away from each other, thereby tending to maintain the centrifugal responsive torque controlled clutch in engagement by a force proportional to the torque of the compression and the pitch of screw threads 96, 91, I23 and I24.

Continued deceleration of the vehicle by the application of the brakes causes a progressive decrease in the centrifugal force actuating weights IiI. When the deceleration of the vehicle has progressed near enough to an actual stop to permit spring H2 urging weights III towards the axis of rotation with sufiicient force to urge pressure disks I530 and IE8 towards each other with a force in excess of the amount of the force with which the decreasing torque of the compression of the motor is urging pressure disks I69 and I98 away from each other, then pressure disks I00 and IE8 are drawn toward each other by springs H2, and the centrifugally responsive torque controlled clutch is promptly disengaged by this action of springs H2 and severance of the driving relationship between the motor and driven shaft I25 is effected.

As this centrifugally responsive torque controlled clutch releases, springs 33 urge pressure plates 55 and II forward, which forward motion is prevented from taking place by the clutch pedal being held in depressed position by the foot pressure of the operator. Therefore, the vehicle stops with the manually operated clutch in release and the motor idling.

Assuming that the vehicle being operated in direct drive, or what is conventionally termed high gear, approaches an incline which the driver desires to descend in what is conventionally known as second gear, then the device will function as follows: In direct drive or high driving connection, the velocity responsive torque controlled clutch mechanism is in engagement, which engagement maintains disengagement of the manually operated clutch mechanism pressure plate ll, clutch plates 55, clutch plates 51 and pressure plate 56. Therefore, the gear train comprising gears 64, 58, BI and 9B, are idling freely. being rotated at a speed which is maintain-ed by the friction on balls 95 in their race between hub section 94 and rim section 9i.

At the moment the operator of the vehicle decides tc' utilize the intermediate or second gear for deceleration, he merely exerts a pull on pull rod I'I'i, which rod acting on lever I 55 pivoted on pivots I 53 of shifting collar I42, moves ratchet clutch-carrying housing I32 forward engaging teeth I33 with teeth I34, permitting plunger I35 to seat in recess I3I, holding teeth I33 and I34 in engagement and then applies the brakes of the vehicle, decelerating it to the predetermined level at which the centrifugal force acting on Weights III is insufficient to maintain compression of springs 33, the expansion of which springs 33 engages the man- 14 ually controlled clutch comprising pressure plates 41, clutch plates 55 and 51 and pressure plate 56, which engagement resiliently connects the clutch housing and driving shaft 20 in driving relation through the intermediate train gears 54, 68, 8| and 90.

Gear is positively engaged with ratchet clutch housing I32 through teeth I33 and I34 and is connected in driving relation with driven shaft I25, unidirectionally clockwise viewed from the rear, by virtue of the splines I30 between flange I29 of driven shaft I25 and ratchet clutch housing I32. Therefore, the decreasing torque of the compression of the motor retarding gear 90 retards driven shaft I25.

In the event that the incline is sufficiently steep to cause the operator of the vehicle to desire to utilize further the compression of the motor by using the low speed gear train after having thus decelerated the vehicle by use of the intermediate speed gear train, he merely utilizes the brake sufficiently to reduce the vehicles speed down to the predetermined level at which the centrifugal force acting on dog 84 is insufficient to maintain in compression springs 86, and then momentarily depresses clutch pedal 45, releasing the manually-operated clutch momentarily, which causes momentary cessation of the tooth pressure exerted by notch I98 of internally notched wheel 89 on tooth 88 of dog 84, whereupon springs 86 immediately pull dog 84 towards its axis of rotation, resulting in seating of tooth 8'! in the opposing notch I99 of externally notched wheel 8%, thereby changing the driving relation between driving shaft 20, the clutch housing and driven shaft I25 from the intermediate gear speed train to the low speed train.

Release of pressure on clutch pedal 45, after' the momentary release of the manually-operated clutch causes said clutch to resiliently connect the motor and driven shaft I25 through the said low speed train, thereby utilizng the mechanical advantage of the 10W speed train to increase the retrograde torque of the compression of the motor on driven shaft I25.

If, at any time while utilizing the intermediate or second speed gear train for retrograde torque inspired by the compression of the motor, the operator desires to again accelerate the vehicle, the following train of events occur.

Release of the brakes of the vehicle and acceleration of the motor immediately remove the retrograde torque operating on gear 89, with the result that gear 90 is impelled to rotate in a counter-clockwise direction. This impulse causes teeth I34 to disengage themselves from teeth I33 by reason of the torque now being counter-clockwise directionally transmitted to driven shaft I25 through the screw threads 96 of hub section 94 and screw threads 91 of shaft 98 instead of clockwise directionally through teeth I33 of ratchet clutch housing I32 and splines I36 between ratchet clutch-carrying housing I32 and flange I29 of driven shaft I25. This, by reason of the fact that the travel of screw threads and screw threads 9?, permit a fraction of rotation of gear 99 counter-clockwise in relation to driven shaft I25 not enjoyed by ratchet clutch-carrying housing I32.

This fraction of rotation permits the inclined plane of the ratchet tooth I34, acting on the inclined plane of ratchet tooth I33, to push ratchet tooth I33 and with it clutch-carrying housing I32 15 rearward to the extent that plunger I36 is raised out of recess I3I. At the moment; of release of plunger I35 from recess I3I, springs 139 immediately force ratchet clutch-carrying housing I32 back to its original position of release. .Therefore it will be seen that the positive engagement unidirectionally clockwise between ratchet carrying housing I32 and gear 9G is automatically disconnected upon the application of counterclockwise torque.

When the operator of the vehicle, while utilizing the low speed or first gear train for retrograde torque inspired by compression of the motor, desires to re-accelerate the vehicle, the mechanism operates as just described and the acceleration proceeds, utilizing the low speed or first gear train until the vehicle has again accelerated to the predetermined level at which the centrifugal force acting upon dog .84 is suificient .to compress springs 86, at which point the operator proceeds to secure the intermediate speed -or second gear, and high speed or direct drive connection in exactly the same manner as described hereinbefore.

Operation of the device in reverse Assuming the vehicle is at a standstill with clutch pedal 45 depressed and the motor running the splined connection 18 between collar T1 and splined hub 16 of gear 69, and to unmesh gear 8| from gear 90 by reason of the fact that collar 11 is prevented from sliding forward on shaft 12 by shoulder I91 of the enlarged forward end of tubular shaft 12.

Thus it will be readily seen that this rearward movement of shaft '12, carrying with it all ofzthe parts mounted thereon rearward -of shoulder I91, produces what is conventionally termed neutral. With this rearward motion of shaft 12 completed, exertion of pull on pull rod I 84 of sufiicient degree to slide hub I53, integral with reversing gears I'M and I15 rearward on shaft I52, a sufficient distance to cause gear I14 to come to mesh with gear 89 and gear I15 to come to mesh with gear 90, simultaneously sufficient pull on pull rod I 7? slides ratchet clutch-carrying casing !32 forward, causing engagement between teeth I33 of the ratchet clutch-carrying housing I32 and teeth I34 of gear 98.

It will be readily seen that thepu'll on the three pull rods just described has served to establish driving connection through "the following gears constituting a reverse gear train, gear 65, gear 69, gear I14, gear H and gear 90, together with the unidirectional positive clutching action of ratchet teeth I33 and I34.

Having completed this operation, release of pressure on clutch pedal 45 by the operator of-the vehicle permits springs 33 to expand, pulling'pressure plate 4? forward, causing resilient engagement between pressure plate 41, clutch plates55, clutch plates 5? and pressure diskifi, which resilient engagement causes the motor t begin to propel the vehicle backwards through the gear .train just described and the unidirectional driving connection of ratchet teeth I33 and I34. When. the operator has backed up :the vehicle the desired distance and wants :to proceed foriii 16 ward again, he brings the vehicle to a stop by application of the brakes and simultaneously depresses clutch pedal 45.

To produce forward driving connections, the operatormerely exerts suflicient pushing pressure on pull rod I84 to slide slidable hub I53 with its integral reversing gears I and I14 forward sufficiently to unmesh ears I15 and I14 from gears .90 and 69, respectively, and then exerts suificient push on pull rod I8! to slide slidable shaft 12 forward'sufiiciently to mesh gear 8| with ,gear and to connect the splined connection I8 between collar '11 and splined hub 16 of gear ,69, after which, release of the pressure on clutch pedal 45, causes engagement of the clutch mechanism previously described as controlled by clutch pedal 45. Forward drive connection in low speed with the motor, is again thus resiliently effected and the vehicle proceeds forward in low gear and henceforth may be operated forward in exactly the same manner as has been described hereinbefore.

In order to avoid excess detail in the drawings which might become confusing, applicant has intentionallyomitted the illustration of any means for lubricating the improved power transmission mechanism. It is considered unnecessary to illustrate means for lubrication since such means are well known to those skiled in the art.

It is now manifest that this is an improvement in :power transmissions, namely, a, device for the transmission of power from a power source such as an engine or a motor to the vehicle, conveyance or machine to be propelled by such a power source, and that it is a power transmissim in which the power from the power source to the vehicle, conveyance or machine propelled is delivered through a series of speed changes through theautomatic inter-position of constantly meshed gear trains .of varying reduction ratios, which inter-position of the various gear trains is effected through the coaction of the velocity of rotation, the torque resistance of the means for propelling the vehicle, conveyance or machine propelled and the torque delivered by the power source, and in which the co-action of the velocity of -rotation,the torque resistance of the means for propelling the vehicle, conveyance or machine propelled and the torque delivered by the power source being inter-opposed and inter-controlled in such manner that the velocity responsive means never escape the opposition or control of the torque responsive means and the torque responsive means never escape the opposition and control of the velocity responsive means.

What I claim is:

.1. Power transmission mechanism of the character disclosed comprising a threaded driven shaft, a disk in .threaded engagement with said shaftand mounted thereon for conjoint rotation therewith, a threaded tubular shaft surrounding :said .driven shaft slidable thereon and rotatable therewithya disk .carried on said tubular shaft positioned in complementary spaced relationship -from the first said disk, both disks having inwardlyinclined converging surfaces, a wedge-shaped weight positioned between said converging inclined surfaces for conjoint rotation therewith endradially slidable by centrifugal force for afclutch means for connecting the second tubular shaft with a source of driving power, and an automatic clutch positioned adjacent the complementary rotary disks for engagement thereby when said disks move away from each other, and positioned to transmit driving power from a prime mover to the first said tubular shaft and to the driven shaft, the disks being urged toward each other by torque applied to the threaded shafts and awayfrom each other by centrifugal force applied through the intermediary of said wedge-shaped weight.

2. Power transmission mechanism of the character disclosed comprising a threaded driven shaft, a disk in threaded engagement with said shaft and mounted thereon for conjoint rotation therewith, a threaded tubular shaft surrounding said driven shaft slidable thereon and rotatable therewith, a disk carried on said tubular shaft positioned in complementary spaced relationship from the first said disk, both disks having inwardly inclined converging surfaces, a wedge shaped weight positioned between said converging inclined surfaces for conjoint rotation therewith and radially slidable by centrifugal force for affecting the spaced relationship of the disks, a hub in threaded engagement with said tubular shaft, a second tubular shaft surrounding the first said tubular shaft, a gear train positioned and adapted to transmit driving torque from the second tubular shaft to the threaded hub, manually operable clutch means for connecting the second tubular shaft with a source of driving power, an automatic clutch positioned adjacent the complementary rotary disks for engagement thereby when said disks move away from each other, and positioned to transmit driving power from a prime mover to the first said tubular shaft and to the driven shaft, the disks being urged tOWard each other by torque applied to the threaded shafts and away from each other by centrifugal force applied through the intermediary of said wedge-shaped weight, and means connected with said manually operable clutch and positioned to be actuated by said separating movement of the disks for releasing the manually perable clutch.

3. Power transmission mechanism of the character disclosed comprising a threaded driven shaft, a disk in threaded engagement with said shaft and mounted thereon for conjoint rotation therewith, a threaded tubular shaft surrounding said driven shaft slidable thereon and rotatable therewith, a disk carried on said tubular shaft positioned in complementary spaced relationship from the first said disk, both disks having inwardly inclined converging surfaces, a wedgeshaped weight positioned between said converging inclined surfaces for conjoint rotation therewith and radially slidable by centrifugal force for affecting the spaced relationship of the disks, a hub in threaded engagement with said tubular shaft, a second tubular shaft surrounding the first said tubular shaft, two gear trains of different ratios positioned and adapted to transmit driving torque from the second tubular shaft to the threaded hub, spring-opposed centrifugal means for alternately effecting engagement of said gear trains, manually operable clutch means for connecting the second tubular shaft with a source of driving power, and an automatic clutch positioned adjacent the complementary rotary disks for engagement thereby when said disks move away from each other, and positioned to transmit driving power from a prime mover to the first said tubular shaft and to the driven shaft, the disks being urged toward each other by torque applied to the threaded shafts and away from each other by centrifugal force applied through the intermediary of said wedge-shaped weight.

4. Power transmission mechanism of the character disclosed comprising a threaded driven shaft, a disk in threaded engagement with said shaft and mounted thereon for conjoint rotation therewith, a threaded tubular shaft surrounding said driven shaft slidable thereon and rotatable therewith, a disk carried on said tubular shaft positioned in complementary spaced relationship from the first said disk, both disks having inwardly inclined converging surfaces, a wedge-shaped weight positioned between said converging inclined surfaces for conjoint rotation therewith and radially slidable by centrifugal force for affecting the spaced relationship of the disks, a hub in threaded en agement with said tubular shaft, a second tubular shaft surrounding the first said, tubular shaft, a gear train positioned and adapted to transmit driving torque from the second tubular shaft to the threaded hub, manually operable clutch means for connecting the second tubular shaft with a source of driving power, selectively shiftable means for transmitting reverse driving torque to the driven shaft, and an automatic clutch positioned adjacent the complementary rotary disks for engagement thereby when said disks move away from each other, and positioned to transmit driving power from a prime mover to the first said tubular shaft and to the driven shaft, the disks being urged toward each other by torque applied to the threaded shafts and away from each other by centrifugal force applied through the intermediary of said wedgeshaped weight.

5. Power transmission mechanism of the character disclosed comprising a threaded driven shaft, a disk in threaded engagement with said shaft and mounted thereon for conjoint rotation therewith, a threaded tubular shaft surrounding said driven shaft slidable thereon and rotatable therewith, a disk carried on said tubular shaft positioned in complementary spaced relationship from the first said disk, both disks having inwardly inclined converging surfaces, a wedgeshaped weight positioned between said converging inclined surfaces for conjoint rotation therewith and radially slidable by centrifugal force for affecting the spaced relationship of the disks, a hub in threaded engagement with said tubular shaft, a second tubular shaft surrounding the first said tubular shaft, two gear trains of different ratios positioned and adapted to transmit driving torque from the second tubular shaft to the threaded hub, spring-opposed centrifugal means for alternately effecting engagement of said gear trains, manually operable clutch means for connecting the second tubular shaft with a source of driving power, selectively shiftable means for transmittin reverse driving torque to the driven shaft, and an automatic clutch positioned adjacent the complementary rotary disks for engagement thereby when said disks move away fromeach other, and positioned to transmit driving-power from a prime mover to the first said tubular shaft and to the driven shaft, the disks being urged toward each other by torque applied to the threaded shafts and away from 

